A&P II Exam 2

Does the body contain more human cells or bacteria cells?

Bacteria --> 10x more

Immune system

not an organ system, but a cell population that inhabits all organs and defends the body from agents of disease

lymphatic system

Network of organs and vein-like vessels that recover fluid, Inspect it for disease agents, Activate immune responses, Return fluid to the bloodstream

How much fluid does the lymphatic system recover?

15% (2 to 4 L/day) of the water and about half of the plasma proteins enter the lymphatic system and then are returned to the blood

What occurs during the fluid recovery?

Immunity and Lipid absorption

Explain what occurs during immunity.

Excess filtered fluid picks up foreign cells and chemicals from the tissues

Passes through lymph nodes where immune cells stand guard against foreign matter

Activates a protective immune response

Explain what occurs during lipid absorption.

Lacteals in small intestine absorb dietary lipids that are not absorbed by the blood capillaries

What are the main two functions of the lymphatic system?

Maintain fluid balance and protect body from infection and disease

What is lymph?

excess tissue fluid carried by lymphatic vessels (the recovered fluid)

-contains much less protein than plasma

What are Lymphatic vessels?

vessels that carry lymph (transport the lymph)

What are lymphatic tissues?

composed of aggregates of lymphocytes and macrophages that populate many organs in the body

What are lymphatic organs?

-Defense cells are especially concentrated in these organs

-Separated from surrounding organs by connective tissue capsules... separates lymphatic tissue from neighboring tissue

Does the chemical composition of lymp vary region to region?

Yes

What is the route of the lymphatic system?

Lymphatic capillaries --> collecting vessels --> lymph trunks --> collecting ducts --> subclavian veins

Where are lymphatic capillaries?

Penetrate nearly every tissue of the body

-Absent from central nervous system, cartilage, cornea, bone, and bone marrow

What are the cells like in the lymphatic capillaries?

Capillary wall is endothelial cells overlapping each other like roof shingles

Cells tethered to surrounding tissue by protein filaments

-Gaps between cells are large enough to allow bacteria and cells to enter lymphatic capillary

What are the "valves" like in the lymphatic capillaries?

Capillaries do not have true valves but...

Endothelium creates valve-like flaps that open when interstitial fluid pressure is high, and close when it is low

Lymphatic vessels have what layers?

Tunica interna: endothelium and valves

Tunica media: elastic fibers, smooth muscle

Tunica externa: thin outer layer

-Larger ones have all three layers

What are the six lymphatic trunks? What do they do?

Jugular, subclavian, broncho mediastinal, intercostal, intestinal (unpaired), and lumbar trunks

They drain major portions of the body

What are the two collecting ducts?

Right lymphatic duct, thoracic duct

Right lymphatic duct does what?

receives lymph from right arm, right side of head and thorax; empties into right subclavian vein

Thoracic duct does what?

larger and longer, begins as a prominent sac in abdomen called the cisterna chyli; receives lymph from below diaphragm, left arm, left side of head, neck, and thorax; empties into left subclavian vein

Where does the thoracic duct empty?

into the left subclavian vein

Where does the right lymphatic duct empty into?

right subclavian vein

How does lymph flow?

It does not have a specific pump for it. Lymph flows at low pressure and slower speed than venous blood.

-Moved along by rhythmic contractions of lymphatic vessels

-Stretching of vessels stimulates contraction

Does pressure have to be high for lymph to flow?

No

What does exercise do to lymphatic return?

increases it

Natural killer (NK) cells

Large lymphocytes that attack and destroy bacteria, transplanted tissue, host cells infected with viruses or that have turned cancerous

(Part of innate immunity)

T Lymphocytes and B lymphocytes are part of what immunity?

adaptive immunity

T lymphocytes

mature in thymus

B lymphocytes

Activation causes proliferation and differentiation into plasma cells that produce antibodies

Mature in bone marrow

Macrophages

Large, avidly phagocytic cells of connective tissue

-Phagocytize tissue debris, dead neutrophils, bacteria, and other foreign matter

-Process foreign matter and display antigenic fragments to certain T cells alerting immune system to the presence of the enemy

What cells are considered APCs (antigen presenting cells)

Macrophages, Dendritic cells, B cells

Dendritic cells

-Branched, mobile APCs found in epidermis, mucous membranes, and lymphatic organs

-Alert immune system to pathogens that have breached the body surface

Reticular cells

Branched stationary cells that contribute to the stroma of a lymphatic organ

What is the difference between stroma and parenchyma?

Stroma is supportive, parenchyma is functional

Diffuse lymphatic tissue

scattered lymphocytes, macrophages, and other cells found deep to mucous membranes

Prevalent in body passages open to the exterior

What is an example of diffuse lymphatic tissue?

Respiratory, digestive, urinary, and reproductive tracts

Mucosa-associated lymphatic tissue (MALT)

Lymphatic nodules (follicles)

-dense masses of lymphocytes and macrophages that congregate in response to pathogens

-constant feature of the lymph nodes, tonsils, and appendix

Peyer patch

Clumps of the nodules... dense clusters in the ileum, the distal portion of the small intestine

What are our primary lymphatic organs?

Red bone marrow and thymus

What are our secondary lymphatic organs?

Lymph nodes, tonsils, and spleen

Red bone marrow

Soft, loosely organized, highly vascular material

-Separated from osseous tissue by endosteum of bone

-As blood cells mature, they push their way through the reticular and endothelial cells to enter the sinus and flow away in the bloodstream

Thymus

Gland in the thoracic cavity above the heart where T lymphocytes mature

member of the endocrine, lymphatic, and immune systems

Does the thymus degenerate with age?

Yes

trabeculae (septa) in the thymus do what?

Fibrous capsule gives off trabeculae (septa) that divide the gland into several lobes

-Lobes have cortex and medulla populated by T lymphocytes

Reticular epithelial cells do what in the thymus?

seal off cortex from medulla forming blood-thymus barrier

-produce signaling molecules

Lymph nodes

most numerous lymphatic organs

-About 450 in typical young adult

What are the two functions of a lymph node?

Cleanse the lymph

Act as a site of T and B cell activation

How is a lymph node shaped?

Elongated, bean-shaped structure with hilum

Enclosed with fibrous capsule with trabeculae that divide interior into compartments

Stroma of reticular fibers and reticular cells

What is the parenchyma of lymph nodes divided into?

cortex and medulla

-Germinal centers where B cells multiply and differentiate into plasma cells

How does lymph leave the node?

through one to three efferent lymphatic vessels that leave the hilum

How does lymph enter the node?

Several afferent lymphatic vessels lead into the node along its convex surface

Are there more afferent or efferent vessels in the lymph nodes?

Way more afferent

90 percent of T cells and B cells that populate the lymph node are delivered how?

in the blood

Cervical lymph nodes

Deep and superficial group in the neck

Monitor lymph coming from head and neck

Axillary lymph nodes

Concentrated in armpit

Receive lymph from upper limb and female breast

Thoracic lymph nodes

In thoracic cavity, especially embedded in mediastinum

Receive lymph from mediastinum, lungs, and airway

Abdominal lymph nodes

Occur in posterior abdominopelvic wall

Monitor lymph from the urinary and reproductive systems

Intestinal and mesenteric lymph nodes

Found in the mesenteries, adjacent to the appendix and intestines

Monitor lymph from the digestive tract

Inguinal lymph nodes

In the groin and receive lymph from the entire lower limb

Popliteal lymph nodes

Occur on the back of the knee

Receive lymph from the leg proper

What happens with metastasis involved with lymphatic vessels?

-Metastasizing cells easily enter lymphatic vessels

-Tend to lodge in the first lymph node they encounter

-Multiply there and eventually destroy the node (Swollen, firm, and usually painless)

-Tend to spread to the next node downstream

What is a treatment of breast cancer?

Treatment of breast cancer is lumpectomy, mastectomy, along with removal of nearby axillary nodes

Tonsils

patches of lymphatic tissue located at the entrance to the pharynx

-Covered with epithelium

-Have deep pits: tonsillar crypts lined with lymphatic nodules

What is the function of tonsils?

Guard against ingested or inhaled pathogens

What is tonsillitis?

Inflammation of the tonsils --> stems from a viral infection

What are the three main sets of tonsils?

-Palatine tonsils

-Lingual tonsils

-Pharyngeal tonsil (adenoids)

What are palatine tonsils?

Pair at posterior margin of oral cavity

Most often infected

What are lingual tonsils?

Pair at root of tongue

What are pharyngeal tonsil (adenoids)?

Single tonsil on wall of nasopharynx

Spleen

the body's largest lymphatic organ

What types of tissues does the parenchyma exhibit?

Red pulp: sinuses filled with erythrocytes (79%)

White pulp: lymphocytes, macrophages surrounding small branches of splenic artery

Functions of the spleen.

-Healthy red blood cells (RBCs) come and go

-For old, fragile RBCs, spleen is "erythrocyte graveyard"

-Blood cell production in fetus (and very anemic adults)

-White pulp monitors blood for foreign antigens and keeps an army of monocytes for release when needed

-Stabilizes blood volume through plasma transfers to lymphatic system

Is the spleen highly vascular?

Yes and vulnerable to trauma and infection

What does a ruptured spleen require?

splenectomy

What lines of defense are considered nonspecific resistance?

1st line of defense and 2nd line of defense

What is the 1st line of defense?

skin and mucous membranes

What is the 2nd line of defense?

nonspecific mechanisms when pathogens break through first line

Protective Cells (leukocytes, macrophages, NK cells) Protective Proteins (interferons, complement)

Protective Processes (fever, inflammation)

What lines of defense are specific or adaptive immunity?

3rd line of defense

What is the 3rd line of defense?

the immune system

Separate immunity to each pathogen, leaves body with "memory" of it so it can defeat it faster in the future

Skin (external barrier)

-Toughness of keratin

-Acid mantle from sweat/sebum that inhibits bacterial growth

-Dermicidin, defensins and cathelicidins: Peptides in the skin that kill microbes

Mucous membranes (external barrier)

Mucus physically traps microbes

Lysozyme: enzyme destroys bacterial cell walls

Sub epithelial areolar tissue (external barrier)

Viscous barrier of hyaluronic acid

What are the 5 types of leukocytes?

neutrophils, eosinophils, basophils, monocytes, lymphocytes

Neutrophils

-Wander in connective tissue killing bacteria

-Can kill using phagocytosis and digestion

-Can kill by producing a cloud of bactericidal chemicals ("respiratory burst" --> Creates a killing zone around neutrophil, destroying several bacteria)

Do neutrophils rise in response to bacterial infection?

Yes

Eosinophils

-Found especially in mucous membranes

-Guard against parasites, allergens (allergy-causing agents), and other pathogens

-Promote action of basophils and mast cells

-Limit action of histamine and other inflammatory chemicals

Basophils

-Secrete chemicals that aid mobility and action of other leukocytes

-Leukotrienes: activate/attract neutrophils and eosinophils

-Histamine: a vasodilator, which increases blood flow

-Heparin: inhibits clot formation

(Mast cells are very similar)

Lymphocytes

-Three basic categories: T, B, and NK cells

-Many diverse functions

Circulating blood contains how many B, T, and NK cells?

80% T cells

15% B cells

5% NK cells

What do NK cells secrete and release?

Release perforins --> Create hole in its plasma membrane Secrete granzymes --> Enter through pore, degrade cellular enzymes

Monocytes

emigrate from the blood into connective tissues and transform into macrophages

Macrophage system

all the body's avidly phagocytic cells, except leukocytes

-Wandering macrophages: actively seek pathogens (widespread in loose connective tissue)

-Fixed macrophages: phagocytize only pathogens that come to them

Two families of antimicrobial proteins

interferons and complement system

What are antimicrobial proteins?

Proteins that inhibit microbial reproduction and provide short-term, nonspecific resistance to pathogenic bacteria and viruses

Interferons

secreted by certain cells infected by viruses

Alert/activate neighboring cells

Bind to surface receptors

Activate 2nd messenger systems within

Alerted cell synthesizes anti-viral proteins

Also activates NK cells and macrophages

Complement system

a group of 30 or more globular proteins that contribute to nonspecific resistance and adaptive immunity

-Synthesized mainly by liver

-Circulate in the blood in inactive form

-Activated by presence of a pathogen

Three routes of complement activation

Classical pathway

Alternative pathway

Lectin pathway

Activated complement system brings about four methods of pathogen destruction

Inflammation

Immune clearance

Phagocytosis

Cytolysis